The transient self-ignition mechanism of PMMA (polymethylmethacrylate) and the effect of combustor shape on self-ignition in solid fuel scramjet with cavity were simulated numerically. An unsteady two-dimensional axisymmetric RANS (Reynolds-averaged Navier-Stokes) equation

SST(shear stress transport) k-ω turbulent model

finite-rate/eddy dissipation reaction model were solved numerically. Main conclusions are as follows: the reactants reach the ignition temperature when the heat of reaction accumulates and increases continuously within the residual time provided by the cavity

so the self-ignition is permitted in solid fuel scramjet. The cavity length

cavity diameter

convergence angle and the cylindrical section diameter of the combustor are the main influential factors to the self-ignition. A step type cavity is suggested to enhance the self-ignition performance.